Generic multi-protocol label switching (GMPLS)-based label space architecture for optical switched networks

ABSTRACT

An architecture and method for performing coarse-grain reservation of lightpaths within wavelength-division-multiplexed (WDM) based photonic burst switched (PBS) networks with variable time slot provisioning. The method employs a generalized multi-protocol label switched (GMPLS)-based PBS label that includes information identifying each lightpath segment in a selected lightpath route. A resource reservation request is passed between nodes during a forward traversal of the route, wherein each node is queried to determine whether it has transmission resources (i.e., a route lightpath segment) available during a future timeframe. Soft reservations are made for each lightpath segment that is available using information contained in a corresponding label. If all lightpath segments for a selected route are available, the soft reservations turn into hard reservations. The stored reservations enable quick routing of control burst that are employed for routing data during scheduled use of the lightpaths.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] The present application is related to U.S. patent applicationSer. No. 10/126,091, filed Apr. 17, 2002; U.S. patent application Ser.No. 10/183,111, filed Jun. 25, 2002; U.S. patent application Ser. No.10/328,571, filed Dec. 24, 2002; U.S. patent application Ser. No.10/377,312 filed Feb. 28, 2003; U.S. patent application Ser. No.10/377,580 filed Feb. 28, 2003; U.S. patent application Ser. No.10/417,823 filed Apr. 16, 2003; U.S. patent application Ser. No.10/417,487 filed Apr. 17, 2003; U.S. Patent Application No. (AttorneyDocket No. 42P16183) filed May 19, 2003, and U.S. Patent Application No.(Attorney Docket No. 42P16552) filed Jun. 18, 2003.

FIELD OF THE INVENTION

[0002] An embodiment of the present invention relates to opticalnetworks in general; and, more specifically, to label space architecturefor generic multi-protocol label switching (GMPLS) within photonicburst-switched networks.

BACKGROUND INFORMATION

[0003] Transmission bandwidth demands in telecommunication networks(e.g., the Internet) appear to be ever increasing and solutions arebeing sought to support this bandwidth demand. One solution to thisproblem is to use fiber-optic networks, wherewavelength-division-multiplexing (WDM) technology is used to support theever-growing demand in optical networks for higher data rates.

[0004] Conventional optical switched networks typically use wavelengthrouting techniques, which require that optical-electrical-optical(O-E-O) conversion of optical signals be done at the optical switches.O-E-O conversion at each switching node in the optical network is notonly very slow operation (typically about ten milliseconds), but it isvery costly, and potentially creates a traffic bottleneck for theoptical switched network. In addition, the current optical switchtechnologies cannot efficiently support “bursty” traffic that is oftenexperienced in packet communication applications (e.g., the Internet).

[0005] A large communication network can be implemented using severalsub-networks. For example, a large network to support Internet trafficcan be divided into a large number of relatively small access networksoperated by Internet service providers (ISPs), which are coupled to anumber of metropolitan area networks (Optical MANs), which are in turncoupled to a large “backbone” wide area network (WAN). The optical MANsand WANs typically require a higher bandwidth than local-area networks(LANs) in order to provide an adequate level of service demanded bytheir high-end users. However, as LAN speeds/bandwidth increase withimproved technology, there is a need for increasing MAN/WANspeeds/bandwidth.

[0006] Recently, optical burst switching (OBS) schemes have emerged as apromising solution to support high-speed bursty data traffic over WDMoptical networks. The OBS scheme offers a practical opportunity betweenthe current optical circuit-switching and the emerging all opticalpacket switching technologies. It has been shown that under certainconditions, the OBS scheme achieves high-bandwidth utilization andclass-of-service (CoS) by elimination of electronic bottlenecks as aresult of the O-E-O conversion occurring at switching nodes, and byusing one-way end-to-end bandwidth reservation scheme with variable timeslot duration provisioning scheduled by the ingress nodes. Opticalswitching fabrics are attractive because they offer at least one or moreorders of magnitude lower power consumption with a smaller form factorthan comparable O-E-O switches. However, most of the recently publishedwork on OBS networks focuses on the next-generation backbone datanetworks (i.e. Internet wide network) using high capacity (i.e., 1 Tb/s)WDM switch fabrics with large number of input/output ports (i.e.,256×256), optical channels (i.e., 40 wavelengths), and requiringextensive buffering. Thus, these WDM switches tend to be complex andvery expensive to manufacture. In contrast, there is a growing demand tosupport a wide variety of bandwidth-demanding applications such asstorage area networks (SANs) and multimedia multicast at a low cost forboth local and wide-area networks.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Non-limiting and non-exhaustive embodiments of the presentinvention are described with reference to the following figures, whereinlike reference numerals refer to like parts throughout the various viewsunless otherwise specified.

[0008]FIG. 1 is a simplified block diagram illustrating a photonicburst-switched (PBS) network with variable time slot provisioning,according to one embodiment of the present invention.

[0009]FIG. 2 is a simplified flow diagram illustrating the operation ofa photonic burst-switched (PBS) network, according to one embodiment ofthe present invention.

[0010]FIG. 3 is a block diagram illustrating a switching node module foruse in a photonic burst-switched (PBS) network, according to oneembodiment of the present invention.

[0011]FIG. 4 is a diagram illustrating the format of an optical databurst for use in a photonic burst-switched network, according to oneembodiment of the present invention.

[0012]FIG. 5 is a diagram illustrating the format of an optical controlburst for use in a photonic burst-switched network, according to oneembodiment of the present invention.

[0013]FIG. 6 is a flow diagram illustrating the operation of a switchingnode module, according to one embodiment of the present invention.

[0014]FIG. 7 is a diagram illustrating PBS optical burst flow betweennodes in a PBS network, according to one embodiment of the presentinvention.

[0015]FIG. 8 is a diagram illustrating generic PBS framing format forPBS optical bursts, according to one embodiment of the presentinvention.

[0016]FIG. 9 is a diagram illustrating a generalized multi-protocollabel switching (GMPLS)-based architecture for a PBS network, accordingto one embodiment of the present invention.

[0017]FIG. 10 is a schematic diagram illustrating an integrated data andcontrol-plane PBS software architecture, according to one embodiment ofthe present invention.

[0018]FIG. 11 is a schematic diagram illustrating PBS softwarearchitecture with the key building blocks a switching node, according toone embodiment of the present invention.

[0019]FIG. 12 is a flowchart illustrating the various operationsperformed in connection with the transmission and processing of controlbursts, according to one embodiment of the present invention.

[0020]FIG. 13 is a block diagram illustrating GMPLS-based PBS labelformat, according to one embodiment of the present invention.

[0021]FIG. 14 is a schematic diagram illustrating an exemplary set ofGMPLS-based PBS labels employed in connection with routing data across aGMPLS-based PBS control network.

[0022]FIGS. 15a and 15 b collectively comprises respective portions of aflowchart illustrating logic and operations performed during a lightpathreservation operations, according to one embodiment of the presentinvention.

[0023]FIG. 16 is a schematic diagram of a PBS switching nodearchitecture, according to one embodiment of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0024] In the following detailed descriptions, embodiments of theinvention are disclosed with reference to their use in a photonicburst-switched (PBS) network. A PBS network is a type of opticalswitched network, typically comprising a high-speed hop andspan-constrained network, such as an enterprise network. The term“photonic burst” is used herein to refer to statistically-multiplexedpackets (e.g., Internet protocol (IP) packets or Ethernet frames) havingsimilar routing requirements. Although conceptually similar tobackbone-based OBS networks, the design, operation, and performancerequirements of these high-speed hop and span-constrained networks maybe different. However, it will be understood that the teaching andprinciples disclosed herein may be applicable to other types of opticalswitched networks as well.

[0025]FIG. 1 illustrates an exemplary photonic burst-switched (PBS)network 10 in which embodiments of the invention described herein may beimplemented. A PBS network is a type of optical switched network. Thisembodiment of PBS network 10 includes local area networks (LANs) 13 ₁-13_(N) and a backbone optical WAN (not shown). In addition, thisembodiment of PBS network 10 includes ingress nodes 15 ₁-15 _(M),switching nodes 17 ₁-17 _(L), and egress nodes 18 ₁-18 _(K) PBS network10 can include other ingress, egress and switching nodes (not shown)that are interconnected with the switching nodes shown in FIG. 1. Theingress and egress nodes are also referred to herein as edge nodes inthat they logically reside at the edge of the PBS network. The edgenodes, in effect, provide an interface between the aforementioned“external” networks (i.e., external to the PBS network) and theswitching nodes of the PBS network. In this embodiment, the ingress,egress and switching nodes are implemented with intelligent modules.This embodiment can be used, for example, as a metropolitan area networkconnecting a large number of LANs within the metropolitan area to alarge optical backbone network.

[0026] In some embodiments, the ingress nodes perform optical-electrical(O-E) conversion of received optical signals, and include electronicmemory to buffer the received signals until they are sent to theappropriate LAN. In addition, in some embodiments, the ingress nodesalso perform electrical-optical (E-O) conversion of the receivedelectrical signals before they are transmitted to switching nodes 17₁-17 _(M) of PBS network 10.

[0027] Egress nodes are implemented with optical switching units ormodules that are configured to receive optical signals from other nodesof PBS network 10 and route them to the optical WAN or other externalnetworks. Egress nodes can also receive optical signals from the opticalWAN or other external network and send them to the appropriate node ofPBS network 10. In one embodiment, egress node 18 ₁ performs O-E-Oconversion of received optical signals, and includes electronic memoryto buffer received signals until they are sent to the appropriate nodeof PBS network 10 (or to the optical WAN).

[0028] Switching nodes 17 ₁-17 _(L) are implemented with opticalswitching units or modules that are each configured to receive opticalsignals from other switching nodes and appropriately route the receivedoptical signals to other switching nodes of PBS network 10. As isdescribed below, the switching nodes perform O-E-O conversion of opticalcontrol bursts and network management control burst signals. In someembodiments, these optical control bursts and network management controlbursts are propagated only on preselected wavelengths. The preselectedwavelengths do not propagate optical “data” bursts (as opposed tocontrol bursts and network management control bursts) signals in suchembodiments, even though the control bursts and network managementcontrol bursts may include necessary information for a particular groupof optical data burst signals. The control and data information istransmitted on separate wavelengths in some embodiments (also referredto herein as out-of-band (OOB) signaling). In other embodiments, controland data information may be sent on the same wavelengths (also referredto herein as in-band (IB) signaling). In another embodiment, opticalcontrol bursts, network management control bursts, and optical databurst signals may be propagated on the same wavelength(s) usingdifferent encoding schemes such as different modulation formats, etc. Ineither approach, the optical control bursts and network managementcontrol bursts are sent asynchronously relative to its correspondingoptical data burst signals. In still another embodiment, the opticalcontrol bursts and other control signals are propagated at differenttransmission rates as the optical data signals.

[0029] Although switching nodes 17 ₁-17 _(L) may perform O-E-Oconversion of the optical control signals, in this embodiment, theswitching nodes do not perform O-E-O conversion of the optical databurst signals. Rather, switching nodes 17 ₁-17 _(L) perform purelyoptical switching of the optical data burst signals. Thus, the switchingnodes can include electronic circuitry to store and process the incomingoptical control bursts and network management control bursts that wereconverted to an electronic form and use this information to configurephotonic burst switch settings, and to properly route the optical databurst signals corresponding to the optical control bursts. The newcontrol bursts, which replace the previous control bursts based on thenew routing information, are converted to an optical control signal, andit is transmitted to the next switching or egress nodes. Embodiments ofthe switching nodes are described further below.

[0030] Elements of exemplary PBS network 10 are interconnected asfollows. LANs 13 ₁-13 _(N) are connected to corresponding ones ofingress nodes 15 ₁-15 _(M). Within PBS network 10, ingress nodes 15 ₁-15_(M) and egress nodes 18 ₁-18 _(K) are connected to some of switchingnodes 17 ₁-17 _(L) via optical fibers. Switching nodes 17 ₁-17 _(L) arealso interconnected to each other via optical fibers in mesharchitecture to form a relatively large number of lightpaths or opticallinks between the ingress nodes, and between ingress nodes 15 ₁-15 _(L)and egress nodes 18 ₁-18 _(K). Ideally, there are more than onelightpath to connect the switching nodes 17 ₁-17 _(L) to each of theendpoints of PBS network 10 (i.e., the ingress nodes and egress nodesare endpoints within PBS network 10). Multiple lightpaths betweenswitching nodes, ingress nodes, and egress nodes enable protectionswitching when one or more node fails, or can enable features such asprimary and secondary route to destination.

[0031] As described below in conjunction with FIG. 2, the ingress,egress and switching nodes of PBS network 10 are configured to sendand/or receive optical control bursts, optical data burst, and othercontrol signals that are wavelength multiplexed so as to propagate theoptical control bursts and control labels on pre-selected wavelength(s)and optical data burst or payloads on different preselectedwavelength(s). Still further, the edge nodes of PBS network 10 can sendoptical control burst signals while sending data out of PBS network 10(either optical or electrical).

[0032]FIG. 2 illustrates the operational flow of PBS network 10,according to one embodiment of the present invention. Referring to FIGS.1 and 2, photonic burst switching network 10 operates as follows.

[0033] PBS network 10 receives packets from LANs 13 ₁-13 _(N). In oneembodiment, PBS network 10 receives IP packets at ingress nodes 15 ₁-15_(M). The received packets can be in electronic form rather than inoptical form, or received in optical form and then converted toelectronic form. In this embodiment, the ingress nodes store thereceived packets electronically. A block 20 represents this operation.

[0034] For clarity, the rest of the description of the operational flowof PBS network 10 focuses on the transport of information from ingressnode 15 ₁ to egress node 18 ₁. The transport of information from ingressnodes 15 ₁-15 _(M) to egress node 18 ₁ (or other egress nodes) issubstantially similar.

[0035] An optical burst label (i.e., an optical control burst) andoptical payload (i.e., an optical data burst) is formed from thereceived packets. In one embodiment, ingress node 15 ₁ uses statisticalmultiplexing techniques to form the optical data burst from the receivedIP (Internet Protocol) packets stored in ingress node 15 ₁. For example,packets received by ingress node 15 ₁ and having to pass through egressnode 18 ₁, on their paths to a destination can be assembled into anoptical data burst payload. A block 21 represents this operation.

[0036] Bandwidth on a specific optical channel and/or fiber is reservedto transport the optical data burst through PBS network 10. In oneembodiment, ingress node 15 ₁ reserves a time slot (i.e., a time slot ofa TDM system) in an optical data signal path through PBS network 10.This time slot maybe fixed-time duration and/or variable-time durationwith either uniform or non-uniform timing gaps between adjacent timeslots. Further, in one embodiment, the bandwidth is reserved for a timeperiod sufficient to transport the optical burst from the ingress nodeto the egress node. For example, in some embodiments, the ingress,egress, and switching nodes maintain an updated list of all used andavailable time slots. The time slots can be allocated and distributedover multiple wavelengths and optical fibers. Thus, a reserved time slot(also referred to herein as a TDM channel), that in differentembodiments may be of fixed-duration or variable-duration, may be in onewavelength of one fiber, and/or can be spread across multiplewavelengths and multiple optical fibers. A block 22 represents thisoperation.

[0037] When an ingress and/or egress node reserves bandwidth or whenbandwidth is released after an optical data burst is transported, anetwork controller (not shown) updates the list. In one embodiment, thenetwork controller and the ingress or egress nodes perform this updatingprocess using various burst or packet scheduling algorithms based on theavailable network resources and traffic patterns. The availablevariable-duration TDM channels, which are periodically broadcasted toall the ingress, switching, and egress nodes, are transmitted on thesame wavelength as the optical control bursts or on a different commonpreselected wavelength throughout the optical network. The networkcontroller function can reside in one of the ingress or egress nodes, orcan be distributed across two or more ingress and/or egress nodes. Inthis embodiment, the network controller is part of control unit 37 (FIG.3), which can include one or more processors.

[0038] The optical control bursts, network management control labels,and optical data bursts are then transported through photonic burstswitching network 10 in the reserved time slot or TDM channel. In oneembodiment, ingress node 15 ₁ transmits the control burst to the nextnode along the optical label-switched path (OLSP) determined by thenetwork controller. In this embodiment, the network controller uses aconstraint-based routing protocol [e.g., multi-protocol label switching(MPLS)] over one or more wavelengths to determine the best availableOLSP to the egress node.

[0039] In one embodiment, the control label (also referred to herein asa control burst) is transmitted asynchronously ahead of the photonicdata burst and on a different wavelength and/or different fiber. Thetime offset between the control burst and the data burst allows each ofthe switching nodes to process the label and configure the photonicburst switches to appropriately switch before the arrival of thecorresponding data burst. The term photonic burst switch is used hereinto refer to fast optical switches that do not use O-E-O conversion.

[0040] In one embodiment, ingress node 15 ₁ then asynchronouslytransmits the optical data bursts to the switching nodes where theoptical data bursts experience little or no time delay and no O-E-Oconversion within each of the switching nodes. The optical control burstis always sent before the corresponding optical data burst istransmitted.

[0041] In some embodiments, the switching node may perform O-E-Oconversion of the control bursts so that the node can extract andprocess the routing information contained in the label. Further, in someembodiments, the TDM channel is propagated in the same wavelengths thatare used for propagating labels. Alternatively, the labels and payloadscan be modulated on the same wavelength in the same optical fiber usingdifferent modulation formats. For example, optical labels can betransmitted using non-return-to-zero (NRZ) modulation format, whileoptical payloads are transmitted using return-to-zero (RZ) modulationformat. The optical burst is transmitted from one switching node toanother switching node in a similar manner until the optical control anddata bursts are terminated at egress node 18 ₁. A block 23 representsthis operation.

[0042] The operational flow at this point depends on whether the targetnetwork is an optical WAN or a LAN. A block 24 represents this branch inthe operational flow.

[0043] If the target network is an optical WAN, new optical label andpayload signals are formed. In this embodiment, egress node 18 ₁prepares the new optical label and payload signals. A block 25represents this operation.

[0044] The new optical label and payload are then transmitted to thetarget network (i.e., WAN in this case). In this embodiment, egress node18 ₁ includes an optical interface to transmit the optical label andpayload to the optical WAN. A block 26 represents this operation.

[0045] However, if in block 24 the target network is a LAN, the opticaldata burst is disassembled to extract the IP packets or Ethernet frames.In this embodiment, egress node 18 ₁ converts the optical data burst toelectronic signals that egress node 18 ₁ can process to recover the datasegment of each of the packets. A block 27 represents this operation.

[0046] The extracted IP data packets or Ethernet frames are processed,combined with the corresponding IP labels, and then routed to the targetnetwork (i.e., LAN in this case). In this embodiment, egress node 18 ₁forms these new IP packets. A block 28 represents this operation. Thenew IP packets are then transmitted to the target network (i.e., LAN) asshown in block 29.

[0047] PBS network 10 can achieve increased bandwidth efficiency throughthe additional flexibility afforded by the TDM channels. Although thisexemplary embodiment described above includes an optical MAN havingingress, switching and egress nodes to couple multiple LANs to anoptical WAN backbone, in other embodiments the networks do not have tobe LANs, optical MANs or WAN backbones. That is, PBS network 10 mayinclude a number of relatively small networks that are coupled to arelatively larger network that in turn is coupled to a backbone network.

[0048]FIG. 3 illustrates a module 17 for use as a switching node inphotonic burst switching network 10 (FIG. 1), according to oneembodiment of the present invention. In this embodiment, module 17includes a set of optical wavelength division demultiplexers 30 ₁-30_(A), where A represents the number of input optical fibers used forpropagating payloads, labels, and other network resources to the module.For example, in this embodiment, each input fiber could carry a set of Cwavelengths (i.e., WDM wavelengths), although in other embodiments theinput optical fibers may carry differing numbers of wavelengths. Module17 would also include a set of N×N photonic burst switches 32 ₁-32 _(B),where N is the number of input/output ports of each photonic burstswitch. Thus, in this embodiment, the maximum number of wavelengths ateach photonic burst switch is A·C, where N≧A·C+1. For embodiments inwhich N is greater than A·C, the extra input/output ports can be used toloop back an optical signal for buffering.

[0049] Further, although photonic burst switches 32 ₁-32 _(B) are shownas separate units, they can be implemented as N×N photonic burstswitches using any suitable switch architecture. Module 17 also includesa set of optical wavelength division multiplexers 34 ₁-34 _(A), a set ofoptical-to-electrical signal converters 36 (e.g., photo-detectors), acontrol unit 37, and a set of electrical-to-optical signal converters 38(e.g., lasers). Control unit 37 may have one or more processors toexecute software or firmware programs. Further details of control unit37 are described below.

[0050] The elements of this embodiment of module 17 are interconnectedas follows. Optical demultiplexers 30 ₁-30 _(A) are connected to a setof A input optical fibers that propagate input optical signals fromother switching nodes of photonic burst switching network 10 (FIG. 10).The output leads of the optical demultiplexers are connected to the setof B core optical switches 32 ₁-32 _(B) and to optical signal converter36. For example, optical demultiplexer 30 ₁ has B output leads connectedto input leads of the photonic burst switches 32 ₁-32 _(B) (i.e., oneoutput lead of optical demultiplexer 30 ₁ to one input lead of eachphotonic burst switch) and at least one output lead connected to opticalsignal converter 36.

[0051] The output leads of photonic burst switches 32 ₁-32 _(B) areconnected to optical multiplexers 34 ₁-34 _(A). For example, photonicburst switch 32 ₁ has A output leads connected to input leads of opticalmultiplexers 34 ₁-34 _(A) (i.e., one output lead of photonic burstswitch 32 ₁ to one input lead of each optical multiplexer). Each opticalmultiplexer also an input lead connected to an output lead ofelectrical-to-optical signal converter 38. Control unit 37 has an inputlead or port connected to the output lead or port ofoptical-to-electrical signal converter 36. The output leads of controlunit 37 are connected to the control leads of photonic burst switches 32₁-32 _(B) and electrical-to-optical signal converter 38. As describedbelow in conjunction with the flow diagram of FIG. 5, module 17 is usedto receive and transmit optical control bursts, optical data bursts, andnetwork management control bursts. In one embodiment, the optical databursts and optical control bursts have transmission formats as shown inFIGS. 4A and 4B.

[0052]FIG. 4A illustrates the format of an optical data burst for use inPBS network 10 (FIG. 1), according to one embodiment of the presentinvention. In this embodiment, each optical data burst has a start guardband 40, an IP payload data segment 41, an IP header segment 42, apayload sync segment 43 (typically a small number of bits), and an endguard band 44 as shown in FIG. 4A. In some embodiments, IP payload datasegment 41 includes the statistically-multiplexed IP data packets orEthernet frames used to form the burst. Although FIG. 4A shows thepayload as contiguous, module 17 transmits payloads in a TDM format.Further, in some embodiments the data burst can be segmented overmultiple TDM channels. It should be pointed out that in this embodimentthe optical data bursts and optical control bursts have localsignificance only in PBS network 10, and may loose their significance atthe optical WAN.

[0053]FIG. 4B illustrates the format of an optical control burst for usein photonic burst switching network 10 (FIG. 1), according to oneembodiment of the present invention. In this embodiment, each opticalcontrol burst has a start guard band 46, an IP label data segment 47, alabel sync segment 48 (typically a small number of bits), and an endguard band 49 as shown in FIG. 4B. In this embodiment, label datasegment 45 contains all the necessary routing and timing information ofthe IP packets to form the optical burst. Although FIG. 4B shows thepayload as contiguous, in this embodiment module 17 transmits labels ina TDM format.

[0054] In some embodiments, an optical network management control label(not shown) is also used in PBS network 10 (FIG. 1). In suchembodiments, each optical network management control burst includes: astart guard band similar to start guard band 46; a network managementdata segment similar to data segment 47; a network management syncsegment (typically a small number of bits) similar to label sync segment48; and an end guard band similar to end guard band 44. In thisembodiment, network management data segment contains network managementinformation needed to coordinate transmissions over the network. In someembodiments, the optical network management control burst is transmittedin a TDM format.

[0055]FIG. 5 illustrates the operational flow of module 17 (FIG. 3),according to one embodiment of the present invention. Referring to FIGS.3 and 5, module 17 operates as follows.

[0056] Module 17 receives an optical signal with TDM label and datasignals. In this embodiment, module 17 receives an optical controlsignal (e.g., an optical control burst) and an optical data signal(i.e., an optical data burst in this embodiment) at one or two of theoptical demultiplexers. For example, the optical control signal may bemodulated on a first wavelength of an optical signal received by opticaldemultiplexer 30 _(A), while the optical data signal is modulated on asecond wavelength of the optical signal received by opticaldemultiplexer 30 _(A). In some embodiments, the optical control signalmay be received by a first optical demultiplexer while the optical datasignal is received by a second optical demultiplexer. Further, in somecases, only an optical control signal (e.g., a network managementcontrol burst) is received. A block 51 represents this operation.

[0057] Module 17 converts the optical control signal into an electricalsignal. In this embodiment, the optical control signal is the opticalcontrol burst signal, which is separated from the received optical datasignal by the optical demultiplexer and sent to optical-to-electricalsignal converter 36. In other embodiments, the optical control signalcan be a network management control burst (previously described inconjunction with FIG. 4B). Optical-to-electrical signal converter 36converts the optical control signal into an electrical signal. Forexample, in one embodiment each portion of the TDM control signal isconverted to an electrical signal. The electrical control signalsreceived by control unit 37 are processed to form a new control signal.In this embodiment, control unit 37 stores and processes the informationcontained in the control signals. A block 53 represents this operation.

[0058] Module 17 then routes the optical data signals (i.e., opticaldata burst in this embodiment) to one of optical multiplexers 34 ₁-34_(A), based on routing information contained in the control signal. Inthis embodiment, control unit 37 processes the control burst to extractthe routing and timing information and sends appropriate PBSconfiguration signals to the set of B photonic burst switches 32 ₁-32_(B) to re-configure each of the photonic burst switches to switch thecorresponding optical data bursts. A block 55 represents this operation.

[0059] Module 17 then converts the processed electrical control signalto a new optical control burst. In this embodiment, control unit 37provides TDM channel alignment so that reconverted or new opticalcontrol bursts are generated in the desired wavelength and TDM time slotpattern. The new control burst may be modulated on a wavelength and/ortime slot different from the wavelength and/or time slot of the controlburst received in block 51. A block 57 represents this operation.

[0060] Module 17 then sends the optical control burst to the nextswitching node in the route. In this embodiment, electrical-to-opticalsignal generator 38 sends the new optical control burst to appropriateoptical multiplexer of optical multiplexers 34 ₁-34 _(A) to achieve theroute. A block 59 represents this operation.

[0061]FIG. 7 illustrates PBS optical burst flow between nodes in anexemplary PBS network 700, according to one embodiment of the presentinvention. System 700 includes ingress node 710, a switching node 712,an egress node 714 and other nodes (egress, switching, and ingress thatare not shown to avoid obscuring the description of the optical burstflow). In this embodiment, the illustrated components of ingress,switching and egress nodes 710, 712 and 714 are implemented usingmachine-readable instructions that cause a machine (e.g., a processor)to perform operations that allow the nodes to transfer information toand from other nodes in the PBS network. In this example, the lightpathfor the optical burst flow is from ingress node 710, to switching node712 and then to egress node 714.

[0062] Ingress node 710 includes an ingress PBS MAC layer component 720having a data burst assembler 721, a data burst scheduler 722, an offsettime manager 724, a control burst builder 726 and a burst framer 728. Inone embodiment, data burst assembler 721 assembles the data bursts to beoptically transmitted over PBS network 10 (FIG. 1). In one embodiment,the size of the data burst is determined based on many different networkparameters such as quality-of-service (QoS), number of available opticalchannels, the size of electronic buffering at the ingress nodes, thespecific burst assembly algorithm, etc.

[0063] Data burst scheduler 722, in this embodiment, schedules the databurst transmission over PBS network 10 (FIG. 1). In this embodiment,ingress PBS MAC layer component 710 generates a bandwidth request forinsertion into the control burst associated with the data burst beingformed. In one embodiment, data burst scheduler 722 also generates theschedule to include an offset time (from offset manager 724 describedbelow) to allow for the various nodes in PBS network 10 to process thecontrol burst before the associated data burst arrives.

[0064] In one embodiment, offset time manager 724 determines the offsettime between the control and data bursts based on various networkparameters such as, for example, the number of hops along the selectedlightpath, the processing delay at each switching node, traffic loadsfor specific lightpaths, and class of service requirements.

[0065] Then control burst builder 726, in this embodiment, builds thecontrol burst using information such as the required bandwidth, burstscheduling time, in-band or out-of-band signaling, burst destinationaddress, data burst length, data burst channel wavelength, offset time,priorities, and the like.

[0066] Burst framer 728 frames the control and data bursts (using theframing format described below in conjunction with FIGS. 7-10 in someembodiments). Burst framer 728 then transmits the control burst over PBSnetwork 10 via a physical optical interface (not shown), as indicated byan arrow 750. In this embodiment, the control burst is transmitted outof band (OOB) to switching node 712, as indicated by an optical controlburst 756 and PBS TDM channel 757 in FIG. 7. Burst framer 728 thentransmits the data burst according to the schedule generated by burstscheduler 722 to switching node 712 over the PBS network via thephysical optical interface, as indicated by an optical burst 758 and PBSTDM channel 759 in FIG. 7. The time delay between optical bursts 756(control burst) and 758 (data burst) in indicated as an OFFSET₁ in FIG.7.

[0067] Switching node 712 includes a PBS switch controller 730 that hasa control burst processing component 732, a burst framer/de-framer 734and a hardware PBS switch (not shown).

[0068] In this example, optical control burst 756 is received via aphysical optical interface (not shown) and optical switch (not shown)and converted to electrical signals (i.e., O-E conversion). Controlburst framer/de-framer 734 de-frames the control burst information andprovides the control information to control burst processing component732. Control burst processing component 732 processes the information,determining the corresponding data burst's destination, bandwidthreservation, next control hop, control label swapping, etc.

[0069] PBS switch controller component 730 uses some of this informationto control and configure the optical switch (not shown) to switch theoptical data burst at the appropriate time duration to the next node(i.e., egress node 714 in this example) at the proper channel. In someembodiments, if the reserved bandwidth is not available, PBS switchcontroller component 730 can take appropriate action. For example, inone embodiment PBS switch controller 730 can: (a) determine a differentlightpath to avoid the unavailable optical channel (e.g., deflectionrouting); (b) delay the data bursts using integrated buffering elementswithin the PBS switch fabric such as fiber delay lines; (c) use adifferent optical channel (e.g. by using tunable wavelength converters);and/or (d) drop only the coetaneous data bursts. Some embodiments of PBSswitch controller component 730 may also send a negative acknowledgmentmessage back to ingress node 710 to re-transmit the dropped burst.

[0070] However, if the bandwidth can be found and reserved for the databurst, PBS switch controller component 730 provides appropriate controlof the hardware PBS switch (not shown). In addition, PBS switchcontroller component 730 generates a new control burst based on theupdated reserved bandwidth from control burst processing component 732and the available PBS network resources. Control burst framer/de-framer734 then frames the re-built control burst, which is then opticallytransmitted to egress node 714 via the physical optical interface (notshown) and the optical switch (not shown), as indicated by PBS TDMchannel 764 and an optical control burst 766 in FIG. 7.

[0071] Subsequently, when the optical data burst corresponding to thereceived/processed control burst is received by switching node 712, thehardware PBS switch is already configured to switch the optical databurst to egress node 714. In other situations, switching node 712 canswitch the optical data burst to a different node (e.g., anotherswitching node not shown in FIG. 7). The optical data burst from ingressnode 710 is then switched to egress node 714, as indicated by PBS TDMchannel 767 and an optical data burst 758A. In this embodiment, opticaldata burst 758A is simply optical data burst 758 re-routed by thehardware PBS switch (not shown), but possibly transmitted in a differentTDM channel. The time delay between optical control burst 766 andoptical data burst 758A is indicated by an OFFSET₂ in FIG. 7, which issmaller than OFFSET₁ due, for example, to processing delay and othertiming errors in switching node 712.

[0072] Egress node 714 includes a PBS MAC component 740 that has a datademultiplexer 742, a data burst re-assembler 744, a control burstprocessing component 746, and a data burst de-framer 748.

[0073] Egress node 714 receives the optical control burst as indicatedby an arrow 770 in FIG. 7. Burst de-framer 748 receives and de-framesthe control burst via a physical O-E interface (not shown). In thisembodiment, control burst processing component 746 processes thede-framed control burst to extract the pertinent control/addressinformation.

[0074] After the control burst is received, egress node 714 receives thedata burst(s) corresponding to the received control burst, as indicatedby an arrow 772 in FIG. 7. In this example, egress node 714 receives theoptical data burst after a delay of OFFSET₂, relative to the end of thecontrol burst. In a manner similar to that described above for receivedcontrol bursts, burst de-framer 748 receives and de-frames the databurst. Data burst re-assembler 744 then processes the de-framed databurst to extract the data (and to re-assemble the data if the data burstwas a fragmented data burst). Data de-multiplexer 742 then appropriatelyde-multiplexes the extracted data for transmission to the appropriatedestination (which can be a network other than the PBS network).

[0075]FIG. 8 illustrates a generic PBS framing format 800 for PBSoptical bursts, according to one embodiment of the present invention.Generic PBS frame 800 includes a PBS generic burst header 802 and a PBSburst payload 804 (which can be either a control burst or a data burst).FIG. 8 also includes an expanded view of PBS generic burst header 802and PBS burst payload 804.

[0076] PBS generic burst header 802 is common for all types of PBSbursts and includes a version number (VN) field 810, a payload type (PT)field 812, a control priority (CP) field 814, an in-band signaling (IB)field 816, a label present (LP) field 818, a header error correction(HEC) present (HP) field 819, a burst length field 822, and a burst IDfield 824. In some embodiments, PBS generic burst header also includes areserved field 820 and a HEC field 826. Specific field sizes anddefinitions are described below for framing format having 32-bit words;however, in other embodiments, the sizes, order and definitions can bedifferent.

[0077] In this embodiment, PBS generic burst header 802 is a 4-wordheader. The first header word includes VN field 810, PT field 812, CPfield 814, IB field 816 and LP field 818. VN field 810 in this exemplaryembodiment is a 4-bit field (e.g., bits 0-3) defining the version numberof the PBS Framing format being used to frame the PBS burst. In thisembodiment, VN field 810 is defined as the first 4-bits of the firstword, but in other embodiments, it need not be the first 4-bits, in thefirst word, or limited to 4-bits.

[0078] PT field 812 is a 4-bit field (bits 4-7) that defines the payloadtype. For example, binary “0000” may indicate that the PBS burst is adata burst, while binary “0001” indicates that the PBS burst is acontrol burst, and binary “0010” indicates that the PBS burst is amanagement burst. In this embodiment, PT field 812 is defined as thesecond 4-bits of the first word, but in other embodiments, it need notbe the second 4-bits, in the first word, or limited to 4-bits.

[0079] CP field 814 is a 2-bit field (bits 8-9) that defines the burst'spriority. For example, binary “00” may indicate a normal priority whilebinary “01” indicates a high priority. In this embodiment, PT field 812is defined bits 8 and 9 of the first word, but in other embodiments, itneed not be bits 8 and 9, in the first word, or limited to 2-bits.

[0080] IB field 816 is a one-bit field (bit 10) that indicates whetherthe PBS control burst is being signaled in-band or OOB. For example,binary “0” may indicate OOB signaling while binary “1” indicates in-bandsignaling. In this embodiment, IB field 816 is defined as bit 10 of thefirst word, but in other embodiments, it need not be bit 10, in thefirst word, or limited to one-bit.

[0081] LP field 818 is a one-bit field (bit 11) used to indicate whethera label has been established for the lightpath carrying this header. Inthis embodiment, LP field 818 is defined as bit 11 of the first word,but in other embodiments, it need not be bit 11, in the first word, orlimited to one-bit.

[0082] HP field 819 is a one-bit (bit 12) used to indicate whetherheader error correction is being used in this control burst. In thisembodiment, HP field 819 is defined as bit 12 of the first word, but inother embodiments, it need not be bit 12, in the first word, or limitedto one-bit. The unused bits (bits 13-31) form field(s) 820 that arecurrently unused and reserved for future use.

[0083] The second word in PBS generic burst header 802, in thisembodiment, contains PBS burst length field 822, which is used to storea binary value equal to the length the number of bytes in PBS burstpayload 804. In this embodiment, the PBS burst length field is 32-bits.In other embodiments, PBS burst length field 822 need not be in thesecond word and is not limited to 32-bits.

[0084] In this embodiment, the third word in PBS generic burst header802 contains PBS burst ID field 824, which is used to store anidentification number for this burst. In this embodiment, PBS burst IDfield 824 is 32-bits generated by the ingress node (e.g., ingress node710 in FIG. 7). In other embodiments, PBS burst ID field 824 need not bein the third word and is not limited to 32-bits.

[0085] The fourth word in PBS generic burst header 802, in thisembodiment, contains generic burst header HEC field 826, which is usedto store an error correction word. In this embodiment, generic burstheader HEC field 826 is 32-bits generated using any suitable known errorcorrection technique. In other embodiments, generic burst header HECfield 826 need not be in the fourth word and is not limited to 32-bits.As in indicated in FIG. 8, generic burst header HEC field 826 isoptional in that if error correction is not used, the field may befilled with all zeros. In other embodiments, generic burst header HECfield 826 is not included in PBS generic burst header 802.

[0086] PBS burst payload 804 is common for all types of PBS bursts andincludes a PBS specific payload header field 832, a payload field 834,and a payload frame check sequence (FCS) field 836.

[0087] In this exemplary embodiment, PBS specific payload header 832 isthe first part (i.e., one or more words) of PBS burst payload 804.Specific payload header field 832 for a control burst is described belowin more detail in conjunction with FIG. 9. Similarly, specific payloadfield 832 for a data burst is described below in conjunction with FIG.9. Typically, specific payload header field 832 includes one or morefields for information related to a data burst, which can be either thisburst itself or contained in another burst associated with this burst(i.e., when this burst is a control burst).

[0088] Payload data field 834, in this embodiment, is the next portionof PBS burst payload 804. In some embodiments, control bursts have nopayload data, so this field may be omitted or contain all zeros. Fordata bursts, payload data field 834 may be relatively large (e.g.,containing multiple IP packets or Ethernet frames).

[0089] Payload FCS field 836, in this embodiment, in the next portion ofPBS burst payload. In this embodiment, payload FCS field 836 is aone-word field (i.e., 32-bits) used in error detection and/orcorrection. As in indicated in FIG. 8, payload FCS field 836 is optionalin that if error detection/correction is not used, the field may befilled with all zeros. In other embodiments, payload FCS field 836 isnot included in PBS burst payload 804.

[0090] In accordance with further aspects of the invention, label spacearchitecture in an extended GMPLS-based framework for a PBS network isprovided. An overview of a GMPLS-based control scheme for a PBS networkin which the label space architecture may be implemented in accordancewith one embodiment is illustrated in FIG. 9. Starting with the GMPLSsuite of protocols, each of the GMPLS protocols can be modified orextended to support PBS operations and optical interfaces while stillincorporating the GMPLS protocols' various traffic-engineering tasks.The integrated PBS layer architecture include PBS data services layer900 on top of a PBS MAC layer 901, which is on top of a PBS photonicslayer 902. It is well known that the GMPLS-based protocols suite(indicated by a block 903 in FIG. 9) includes a provisioning component904, a signaling component 905, a routing component 906, a labelmanagement component 907, a link management component 908, and aprotection and restoration component 909. In some embodiments, thesecomponents are modified or have added extensions that support the PBSlayers 900-902. Further, in this embodiment, GMPLS-based suite 903 isalso extended to include an operation, administration, management andprovisioning (OAM&P) component 910. Further information on GMPLSarchitecture can be found athttp://www.ietf.org/internet-drafts/draft-ietf-ccamp-gmpls-architecture-07.txt.

[0091] For example, signaling component 905 can include extensionsspecific to PBS networks such as, for example, burst start time, bursttype, burst length, and burst priority, etc. Link management component908 can be implemented based on the well-known link management protocol(LMP) (that currently supports only SONET/SDH networks), with extensionsadded to support PBS networks. Protection and restoration component 909can, for example, be modified to cover PBS networks. Further informationon LMP can be found athttp://www.ietf.org/internet-drafts/draft-ietf-ccamp-lmp-09.txt.

[0092] Further, for example, label management component 907 can bemodified to support a PBS control channel label space. In oneembodiment, the label operations are performed after control channelsignals are O-E converted. The ingress nodes of the PBS network act aslabel edge routers (LERs) while the switching nodes act as label switchrouters (LSRs). An egress node acts as an egress LER substantiallycontinuously providing all of the labels of the PBS network. An ingressnode can propose a label to be used on the lightpath segment it isconnected to, but the downstream node will be the deciding one inselecting the label value, potentially rejecting the proposed label andselecting its own label. A label list can also be proposed by a node toits downstream node. This component can advantageously increase thespeed of control channel context retrieval (by performing apre-established label look-up instead of having to recover a fullcontext). Further details of label configuration and usage are discussedbelow.

[0093] To enable PBS networking within hop and span-constrainednetworks, such as enterprise networks and the like, it is advantageousto extend the GMPLS-based protocols suite to recognize the PBS opticalinterfaces at both ingress/egress nodes and switching nodes. Under theGMPLS-based framework, the PBS MAC layer is tailored to perform thedifferent PBS operations while still incorporating the MPLS-basedtraffic engineering features and functions for control burst switchingof coarse-grain (from seconds to days or longer) optical flowsestablished using a reservation protocol and represented by a PBS label.

[0094]FIG. 10 shows an integrated data and control-plane PBS softwarearchitecture 1000 with the key building blocks at ingress/egress nodes.Data plane components in architecture 1000 includes a flowclassification block 1002, and L3 (Layer 3, i.e. the Internet layer inthe networking stack) forwarding block 1004, a label processing block1006, a queue management block 1008, a flow scheduler 1010, and legacyinterfaces 1012. In addition, the data plane components include theingress node 710 and egress node 714 components discussed above withreference to FIG. 7. GMPLS-based functionality is implemented in thecontrol plane, which includes link management component 908, signalingcomponent 904, protection and restoration component 909, OAM & Pcomponent 910, and routing component 906. GMPLS signaling functionaldescription can be found at http://www.ietf.org/rfc/rfc3471.txt.

[0095] On the data path, packets from legacy interfaces 1012, (i.e., IPpackets or Ethernet frames) are classified by flow classification block1002 based on n-tuples classification into forward-equivalent classes(FECs) 1014 at the ingress/egress node. Specifically, an adaptive PBSMAC layer at the ingress node typically performs data burst assembly andscheduling, control burst generation, and PBS logical framing, whilede-framing, de-fragmentation and flow de-multiplexing are performed atthe egress node. Once classified, data corresponding to a given FEC isforwarded to L3 forward block 1004. If the flow is for this node IPaddress, i.e. this node L3 address then the flow is given to this nodefor processing, i.e., it is given to this node control plane to beprocessed.

[0096] The next operations concern flow management. These are handled bylabel processing block 1006, as described below in further detail, andqueue management block 1008. Timing of when portions of data destinedfor legacy network components are sent is determined by flow scheduler1010.

[0097]FIG. 11 illustrates PBS software architecture 1100 with the keybuilding blocks at the switching nodes. The software architectureincludes a control burst processing block 1102, a contention resolutionblock 1104, a burst control block 1106, a PBS switch configuration andcontrol block 1108, and a resource manager block 1110. Operationsprovided by blocks 1102, 1104, 1106, 1108, and 1110 are performed bycorrespond sets of software (i.e. machine-executable instructions) thatare executed by a PBS control processor 1112.

[0098] Control burst processing block 1102 performs bandwidthreservation, next hop selection, label-switched-path (LSP) setup in, andcontrol label swapping accordance with GMPLS-based framework. Contentionresolution block 1104 performs deflection routing, provides tunablewavelength conversion, NACK (negative acknowledgement)/drop functionsand fiber delay line (FDL) operations. Burst control block 1106 providesupdated control packets. PBS switch configuration and control block 1108provides configuration and control of the PBS switch controlled by PBScontrol processor 1112. Resource manager block 1110 performs resourcemanagement operations, including updating network resources (bandwidthused on each wavelength, total wavelength utilization, etc).

[0099] The transmitted PBS control bursts, which are processedelectronically by the PBS Network processor (NP), undergo the followingoperations: With reference to the flowchart of FIG. 12, the processbegins in a block 1200, wherein the control burst is de-framed,classified according to its priority, and the bandwidth reservationinformation is processed. If an optical flow has been signaled andestablished this flow label is used to lookup the relevant information.Next, in a block 1202, the PBS switch configuration settings for thereserved bandwidth on the selected wavelength at a specific time iseither confirmed or denied. If confirmed, the process proceeds; ifdenied, a new reservation request process is initiated.

[0100] In a block 1204, PBS contention resolution is processed in caseof PBS switch configuration conflict. One of the three possiblecontention resolution schemes, namely FDL-based buffering, tunablewavelength converters, and deflection routing can be selected. If noneof these schemes are available, the incoming data bursts are droppeduntil the PBS switch becomes available and a negative acknowledgementmessage is sent to the ingress node to retransmit. A new control burstis generated in a block 1206, based on updated network resourcesretrieved from the resource manager, and scheduled for transmission. Thenew control burst is then framed and placed in the output queue fortransmission to the next node in a block 1208.

[0101] In important aspect of the present invention pertains to labelsignaling, whereby coarse-grain lightpaths are signaled end-to-end andassigned a unique PBS label. The PBS label has only lightpath segmentsignificance and not end-to-end significance. In exemplary PBS labelformat 1300 is shown in FIG. 13 with its corresponding fields, furtherdetails of which are discussed below. The signaling of PBS labels forlightpath set-up, tear down, and maintenance is done through anextension of IETF (internet engineering task force) resource reservationprotocol-traffic engineering (RSVP-TE). More information on GMPLSsignaling with RSVP-TE extensions can be found athttp://www.ietf.org/rf/rfc3473.txt.

[0102] The PBS label, which identifies the data burst input fiber,wavelength, and lightpath segment, channel spacing, is used on thecontrol path to enable one to make soft reservation request of thenetwork resources (through corresponding RESV messages). If the requestis fulfilled (through the PATH message), each switching node along theselected lightpath commits the requested resources, and the lightpath isestablished with the appropriate segment-to-segment labels. Eachswitching node is responsible for updating the initial PBS label throughthe signaling mechanism, indicating to the previous switching node thelabel for its lightpath segment. If the request cannot be fulfilled oran error occurred, a message describing the condition is sent back tothe originator to take the appropriate action (i.e., select anotherlightpath characteristics). Thus, the implementation of the PBS labelthrough signaling enables an MPLS type efficient lookup for the controlburst processing. This processing improvement of the control burst ateach switching node reduces the required offset time between the controland data bursts, resulting in an improved PBS network throughput andreduced end-to-end latency.

[0103] In addition to the software blocks executed by the PBS controlprocessor, there are several other key components that support PBSnetworking operations described herein. Link Management component 908 isresponsible for providing PBS network transport link status informationsuch as link up/down, loss of light, etc. The component runs its ownlink management protocol on the control channel. In one embodiment, theIETF link management protocol (LMP) protocol is extended to support PBSinterfaces. Link protection and restoration component 909 is responsiblefor computing alternate optical paths among the various switching nodesbased on various user-defined criteria when a link failure is reportedby the link management component. OAM&P component 910 is responsible forperforming various administrative tasks such as device provisioning.

[0104] Additionally, routing component 906 provides routing informationto establish the route for control and data burst paths to their finaldestination. For PBS networks with bufferless switch fabrics, thiscomponent also plays an important role in making PBS a more reliabletransport network by providing backup route information that is used toreduce contention.

[0105] The label signaling scheme of the present invention reduces thePBS offset time by reducing the amount of time it takes to process asignaled lightpath. This is achieved by extending the GMPLS model toidentify each lightpath segment within the PBS network using a uniquelabel defined in a PBS label space. The use of a PBS label speeds up thePBS control burst processing by allowing the control interface unitwithin the PBS switching node, which processes the control burst, tolookup relevant physical routing information and other relevantprocessing state based on the label information used to perform a fastand efficient lookup. Thus, each PBS switching node has access in onelookup operation to the following relevant information, among others: 1)the address of the next hop to send the control burst to; 2) informationabout the outgoing fiber and wavelength; 3) label to use on the nextsegment if working in a label-based mode; and 4) data needed to updatethe scheduling requirement for the specific input port and wavelength.

[0106] Returning to FIG. 13, in one embodiment PBS label 1300 comprisesfive fields, including an input fiber port field 1302, a inputwavelength field 1304, a lightpath segment ID field 1306, a channelspacing (Δ) field 1308, and a reserved field 1310. The input fiber portfield 1302 comprises an 8-bit field that specifies the input fiber portof the data channel identified by the label (which itself is carried onthe control wavelength. The input wavelength field 1304 comprises a32-bit field that describes the input data wavelength used on the inputfiber port specified by input fiber port field 1302, and is described infurther detail below. The lightpath segment ID field 1306 comprises a16-bit field that describes the lightpath segment ID on a specificwavelength and a fiber cable. Lightpath segment ID's are predefinedvalues that are determined based on the PBS network topology. Thechannel spacing field 1308 comprises a 4-bit field used for identifyingthe channel spacing (i.e., separation between adjacent channels) (inconnection with the Δ variable defined below. The reserved field 1310 isreserved for implementation-specific purposes and future expansion.

[0107] In one embodiment, the input wavelength is represented using IEEE(Institute of Electrical and Electronic Engineers) standard 754 forsingle precision floating-point format. The 32-bit word is divided intoa 1-bit sign indicator S, an 8-bit biased exponent e, and a 23-bitfraction. The relationship between this format and the representation ofreal numbers is given by: $\begin{matrix}{{Value} = \{ \begin{matrix}{{( {- 1} )^{S} \cdot ( 2^{e - 127} ) \cdot ( {1 + f} )}} & {{{normalized},{0 < e < 255}}} \\{( {- 1} )^{S} \cdot ( 2^{e - 126} ) \cdot ( {0 + f} )} & {{{{de}{normalized}},{e = 0},{f > 0}}} \\{{{exceptional}\quad {value}}} & {otherwise}\end{matrix} } & {{Eq}.\quad (1)}\end{matrix}$

[0108] One of the optical channels in the C band has a frequency of197.200 THz, corresponding to a wavelength of 1520.25 nm. This channelis represented by setting s=0, e=134, and f=0.540625. The adjacentchannel separation can be 50 GHz, 100 GHz, 200 GHz, or other spacing.For 50 GHz channel separation, it can be written as: Δ=0.05=1.6·2⁻⁵(s=0, e=122, f=0.6). Thus, the wavelength of the nth channel is givenby:

f(n)=f(1)−(n−1)·Δ  Eq. (2)

[0109] Thus, according to equation (2), the optical channel frequency isgiven by n and the specific value of Δ, which can be provided as part ofthe initial network set-up. For example, using the standard ITU-T(International Telecommunications Union) grid C and L bands, n islimited to 249, corresponding to an optical frequency of 184.800 THz.However, other optical channel frequencies outside the above-mentionedrange or other wavelength ranges such as wavelength band around 1310 nmcan be also defined using equation (2).

[0110] Operation of how PBS label 1300 is implemented in a GMPLS-basedPBS network 1400 is illustrated in FIG. 14. Network 1400, which maycomprise one of various types of networks, such as an enterprisenetwork, contains six PBS switching nodes, respectively labeled A, B, C,D, E, and F. Network 1400 is coupled at one end to a LAN or WAN network1402 and a LAN or WAN network 1404 at another end, wherein edge nodes Aand D operate as edge nodes. For the following example, it is desired toroute traffic from network 1402 to network 1404. Accordingly, edge nodeA (a.k.a., the source node) operates as an ingress node, while edge nodeD (a.k.a., the destination node) operates as an egress node.

[0111] The various switching nodes B, C, E, and F are coupled bylightpath segments LP1, LP2, LP3, LP4, LP5, LP6, LP7, LP8 and LP9, asshown in FIG. 14. There are also other lightpath segmentscross-connecting switching nodes B, C, E, and F, which are not shown forclarity. A lightpath segment comprises an optical coupling via opticalfibers between any adjacent nodes. A lightpath comprises the pathtraveled between source and destination nodes, and typically willcomprises a plurality of lightpath segments. In the illustrated example,the lightpath between the source node (ingress node A) and thedestination node (egress node D) dynamically selected at signaling time,through the use of a well known signaling protocol such as RSVP-TE,comprises lightpath segments LP1, LP4, and LP6.

[0112] As further shown in FIG. 14, exemplary PBS labels A-B-0 and A-B-1are assigned to the path between nodes A and B at times t₀ and t₁,respectively; labels B-C-0 and B-C-1 are assigned to the path betweennodes B and C nodes at times t₀ and t₁; and labels C-D-0 and C-D-1 areassigned to the path between nodes C and D nodes at times t₀ and t₁. Forthe purpose of simplicity, the lightpath segment ID's for lightpathsegments LP1, LP2, LP3, LP4, LP5 and LP6 are respectively defined as0x0001, 0x0002, 0x0003, 0x0004, 0x0005, and 0x0006. In accordance withforegoing aspects of PBS networks, a particular LSP may compriselightpath segments employing different wavelengths. As such, in theillustrated example label A-B-0 defines the use of an optical frequencyof 197.2 THz (0x08683FD1), label B-C-0 defines the use of a frequency of196.4 THz (0x08682767), and label C-D-0 defines the use of a frequencyof 195.6 THz (0x08680EFD). On the way from A to D the signaling packetrequests resource reservation on a lightpath segment-by-segment basis(i.e. LP1, LP4, LP6). For example, edge node A requests resources tocreate a coarse-grain reservation of a selected lightpath. On the firstlightpath segment, switching node B checks if it has sufficientresources to satisfy the request. If it doesn't have the resources, itsends an error message back to the originator of the request to take theappropriate action such as send another request or select anotherlightpath. If it has enough resources, it makes a soft reservation ofthese resources, and forwards it to the next switching node, wherein theoperations are repeated until the destination node D is reached. Whennode D receives the soft reservation request, it checks if it can befulfilled.

[0113] With reference to the flowchart of FIGS. 15a and 15 b, operationsand logic performed during a PBS label-based lightpath reservationprocess in accordance with one embodiment of the invention proceeds asfollows. The process begins at a source node (e.g., source node A),which initiatives the first operation in a block 1501, wherein alightpath between the source and destination nodes is selected. Forexample, the RSVP-TE (IETF RFC 3209) protocol may be used in oneembodiment to automatically determine one or more lightpaths from whichto choose a selected lightpath. In this instance, the IP address of thedestination node is provided, and the protocol navigates the networktopology from the source node to the destination node to determinelightpath segment combinations that may be connected to reach thedestination node. Optionally, an explicit route corresponding to alightpath that traverses a plurality of lightpath segments may bespecified using the EXPLICIT_ROUTE object, which encapsulates aconcatenation of hops which constitutes the explicitly routed path.Lightpath selection techniques of this sort are well-known in the art,so no further explanation of how this operation is performed is includedherein. In accordance with the current example, a lightpath traversinglightpath segments LP1 to LP4 to LP6 is selected.

[0114] In a block 1502, an initial PBS label for a first lightpathsegment (LP1) between the source node and the first switching node (nodeB) is created. As shown in FIG. 13 and discussed above, the labelidentifies an input fiber port, input wavelength, and lightpath segmentID corresponding to lightpath segment LP1. A resource reservationrequest containing the initial PBS label is then sent to the firstswitching node. In one embodiment, the passing of the resourcereservation request between nodes is performed via a signaling packet.

[0115] The next set of operations and logic are performed in a loopingmanner, as indicated by start and end loop blocks 1503 and 1504,starting at switching node B, which comprises the first switching nodeon the ingress side of the lightpath. The operations defined betweenstart and end loop blocks 1503 and 1504 are performed in an iterativemanner for each switching node, until the last lightpath segment hasbeen evaluated for availability. As used herein, the term “current node”identifies that the operations are being performed at a node for whichthe evaluated lightpath segment is received. The term “next node”represents the next node in the lightpath chain. When the logic loopsback to start loop block 1503 from end loop block 1503, the next nodebecomes the current node.

[0116] In a block 1506 the resource reservation request received by thenode is accessed to identify the current lightpath segment. In adecision block 1508, a determination is made by the node to whether ithas sufficient resources to satisfy the request. In addition to thelabel information, the resource reservation request specifies atimeframe for which the reservation corresponds. An indication ofsufficient resources means that the specified resource (i.e., thelightpath segment received at the current node) has not been previouslyscheduled for use over any portion of the specified timeframe. Ifsufficient resources are not available, the answer to decision block1508 is NO, and the logic proceeds to a block 1510 in which an errormessage is sent back to the originator of the request (i.e., the sourcenode). In response, the source node performs an appropriate action, suchas sending a new request via another lightpath.

[0117] If there are sufficient resources to satisfy the reservationrequest, the logic proceeds to a block 1514 in which a soft reservationis made for the current lightpath segment. In one embodiment, the softreservation is stored in a reservation table, such as that describedbelow in further detail, wherein an exemplary soft reservation tableentry is shown at time instance 1406A in FIG. 14. The soft reservationcontains a reference to the current lightpath segment, via a LightpathSegment ID field 1414. This reference will be subsequently used duringfast routing lookup table operations in accordance with control bursts.

[0118] Next, a determination is made in a decision block 1515 to whetherthe destination node has been reached. If it has, the logic proceeds tothe next portion of the flowchart illustrated in FIG. 15b. If it hasnot, the logic proceeds to a block 1516, wherein the PSB label isupdated for the next lightpath segment. Exemplary labels are shown atthe lower portion of FIG. 14 and discussed below. The updated label willnow reference the lightpath segment ID for the next lightpath segment inthe change, including new input fiber port, and wavelength values. Theresource reservation request containing the updated label is thenforwarded to the next node via the signaling mechanism in accordancewith end loop block 1504. As discussed above, the operations in blocks1506, 1508, 1510, 1512, 1514, 1515, and 1516 are then repeated, asappropriate, in an iterative manner until the destination node isreached, resulting in a YES result for decision block 1515.

[0119] Proceeding to the portion of the flowchart shown in FIG. 15b, atthis point the current node is the destination node D, as depicted by astart block 1520. As before, operations are repeated for each of thenodes along the selected lightpath, akin to a back-propagationtechnique; these operations are delineated by start and end loop blocks1522 and 1523. First, in a block 1524, the software reservation for thecurrent node is upgraded to a hard reservation, and the correspondingresources are committed. This is reflected by changing the value in areservation status (Status) field 1420 from a “0” (soft) to a “1”(hard).

[0120] Following the operation of block 1526, a determination is made towhether the source node has been reached. If it has, the process iscompleted, and all segments on the lightpath are reserved for asubsequent scheduled use. If not, the process repeats itself for thenext (now current) switching node until the source node is reached. Atthis point, all the nodes along the lightpath will have hard (i.e.,confirmed) reservations, and the entire lightpath will be scheduled foruse during the indicated timeframe contained in the reservation table.

[0121] Time-based instances (i.e., time snapshots) 1406A and 1406B of anexemplary reservation table are shown in FIG. 14. The reservation tableincludes a (optional) key field 1408, an input fiber port 1410, an inputwavelength field 1412, lightpath segment ID field 1414, a start timefield 1416, and end time field 1418, and reservation status field 1420.In addition to the fields shown, the reservation table may typicallyinclude other related information. Furthermore, for illustrativepurposes only a time of day value is shown in the start and end timefields. Actually fields would include information identifying the date,or the start and end times could be further divided such that start andend date fields are provided.

[0122] When the PBS label information is transmitted (e.g., from node Ato node D), a soft reservation is made at nodes B, C, and D, asdescribed above. Time instance 1406A corresponds to a snapshot of thereservation table at node C is shown in FIG. 14 shortly after a softreservation has been made. In this case, the reservation status (Status)field value, which comprises a Boolean value, is set to 0, indicatingthe reservation is not confirmed (i.e., a soft reservation). In timeinstance 1406B corresponds to the change in the table that is made toreservation status field 1420 when the reservation is confirmed on thereturn path from node D to node A).

[0123] As further indicated by the labels depicted in FIG. 14, thelabels for a given node pair may change over time to reflect a change inthe lightpath routing or network topology. Consider the PBS label valuesfor times t₀ and t₁. The PBS labels at t₀ indicate a lightpath route ofLP1 to LP4 to LP6, using wavelengths of 197.2 THz, 196.4 THz, and 195.6THz, respectively. In contrast, at t₁ a portion of the routing path andfrequencies have been changed, such that the lightpath route is LP1 toLP4 to LP5, using wavelengths of 197.2 THz, 195.6 THz, and 195.6 THz.

[0124] A simplified block diagram 1600 of a PBS switching nodearchitecture in accordance with one embodiment is shown in FIG. 16. Theintelligent switching node architecture is logically divided intocontrol plane components and data plane. The control plane includes acontrol unit 37 employing a network processor (NP) 1602, coupled to gluelogic 1604 and a control processor (CPU) 1606 that runs softwarecomponents stored in a storage device 1607 to perform the GMPLS controloperations 1608 disclosed herein. Network processor 1602 is also coupledto one or more banks of SDRAM (synchronous dynamic random access memory)memory 1610, which is used for general memory operations. The data planearchitecture comprises a non-blocking optical switch fabric comprising aPBS 32, coupled optical multiplexers 1612, de-multiplexers 1614, andoptical transceivers (as depicted by an optical receiver (Rx) block 1616and an optical transmitter (Tx) block 1618).

[0125] The burst assembly and framing, burst scheduling and control,which are part of the PBS MAC layer and related tasks are performed bynetwork processor 1602. Network processors are very powerful processorswith flexible micro-architecture that are suitable to support wide-rangeof packet processing tasks, including classification, metering,policing, congestion avoidance, and traffic scheduling. For example, theIntel® IXP2800 NP, which is used in one embodiment, has 16 microenginesthat can support the execution of up to 1493 microengines instructionsper packet at a packet rate of 15 million packets per second for 10 GbEand a clock rate of 1.4 GHz.

[0126] In one embodiment, the optical switch fabric has strictlynon-blocking space-division architecture with fast (<100 ns) switchingtimes and with limited number of input/output ports (e.g., ≈8×8, 12×12).Each of the incoming or outgoing fiber links typically carries only onedata burst wavelength. The switch fabric, which has no or limitedoptical buffering fabric, performs statistical burst switching within avariable-duration time slot between the input and output ports. Theoptical buffering can be implemented using fiber-delay-lines (FDLs) onseveral unused ports, such as taught in L. Xu, H. G. Perros, and G.Rouskas, “Techniques for Optical Packet Switching and Optical BurstSwitching,” IEEE Communication Magazine 1, 136-142 (2001). The specificoptical buffering architecture, such as feed-forward or feedback, willgenerally depend on the particular characteristics of the switching nodeand PBS network in which it is deployed. However, the amount ofbuffering is expected to be relatively small compared with conventionalpacket switching fabric, since the FDLs can carry multiple data burstwavelengths. Other possible contention resolution schemes includedeflection routing and using tunable wavelength converters, as discussedabove. In one embodiment, contention resolution schemes disclosed by D.J. Blumenthal, B. E. Olson, G. Rossi, T. E. Dimmick, L. Rau, M.Masanovic, O. Lavrova, R. Doshi, O. Jerphagnon, J. E. Bowers, V. Kaman,L. Coldren, and J. Barton, “All-Optical Label Swapping Networks andTechnologies,” IEEE J. of Lightwave Technology 18, 2058-2075 (2000) maybe implemented. The PBS network can operate with a relatively smallnumber of control wavelengths (λ′₀, λ₀), since they can be shared amongmany data wavelengths. Furthermore, the PBS switch fabric can alsooperate with a single wavelength and multiple fiber; however, furtherdetails of this implementation are not disclosed herein.

[0127] The control bursts can be sent either in-band (IB) or out of band(OOB) on separate optical channels. For the OOB case, the optical databursts are statistically switched at a given wavelength between theinput and output ports within a variable time duration by the PBS fabricbased on the reserved switch configuration as set dynamically by networkprocessor 1602. NP 1602 is responsible to extract the routinginformation from the incoming control bursts, providing fix-durationreservation of the PBS switch resources for the requested data bursts,and forming the new outgoing control bursts for the next PBS switchingnode on the path to the egress node. In addition, the network processorprovides overall PBS network management functionality based on thenextended GMPLS-based framework discussed above. For the IB case, boththe control and data bursts are transmitted to the PBS switch fabric andcontrol interface unit. However, NP 1602 ignores the incoming databursts based on the burst payload header information. Similarly, thetransmitted control bursts are ignored at the PBS fabric since theswitch configuration has not been reserved for them. One advantage ofthis approach is that it is simpler and cost less to implement since itreduces the number of required wavelengths.

[0128] Another approach for IB signaling is to use different modulationformats for the control bursts and the data bursts. For example, thecontrol bursts are non-return to zero (NRZ) modulated while the databursts are return to zero (RZ) modulated. Thus, only the NRZ controlbursts are demodulated at the receiver in the PBS control interface unitwhile the RZ data bursts are ignored.

[0129] Embodiments of method and apparatus for implementing a photonicburst switching network are described herein. In the above description,numerous specific details are set forth to provide a thoroughunderstanding of embodiments of the invention. One skilled in therelevant art will recognize, however, that embodiments of the inventioncan be practiced without one or more of the specific details, or withother methods, components, materials, etc. In other instances,well-known structures, materials, or operations are not shown ordescribed in detail to avoid obscuring this description.

[0130] Reference throughout this specification to “one embodiment” or“an embodiment” means that a particular feature, structure, orcharacteristic described in connection with the embodiment is includedin at least one embodiment of the present invention. Thus, theappearances of the phrases “in one embodiment” or “in an embodiment” invarious places throughout this specification are not necessarily allreferring to the same embodiment. Furthermore, the particular features,structures, or characteristics may be combined in any suitable opticalmanner in one or more embodiments.

[0131] Thus, embodiments of this invention may be used as or to supportsoftware program executed upon some form of processing core (such as theCPU of a computer or a processor of a module) or otherwise implementedor realized upon or within a machine-readable medium. A machine-readablemedium includes any mechanism for storing or transmitting information ina form readable by a machine (e.g., a computer). For example, amachine-readable medium can include such as a read only memory (ROM); arandom access memory (RAM); a magnetic disk storage media; an opticalstorage media; and a flash memory device, etc. In addition, amachine-readable medium can include propagated signals such aselectrical, optical, acoustical or other form of propagated signals(e.g., carrier waves, infrared signals, digital signals, etc.).

[0132] In the foregoing specification, embodiments of the invention havebeen described. It will, however, be evident that various modificationsand changes may be made thereto without departing from the broaderspirit and scope as set forth in the appended claims. The specificationand drawings are, accordingly, to be regarded in an illustrative ratherthan a restrictive sense.

What is claimed is:
 1. A method for establishing a coarse-grainedreservation of a lightpath traversing a plurality of lightpath segmentscoupled between nodes in an optical switched network, comprising:passing a resource reservation request containing a generalizedmulti-protocol label-switching (GMPLS)-based label to each of the nodestraversed by the lightpath, the GMPLS-based label identifying alightpath segment to which each node is coupled; and reserving each ofthe of lightpath segments for a scheduled timeframe with a respectivelightpath segment reservation, each lightpath segment reservationreferencing its corresponding lightpath segment using data contained inthe GMPLS-based label.
 2. The method of claim 1, wherein the opticalswitched network comprises a photonic burst switched (PBS) network. 3.The method of claim 2, wherein the optical burst switched networkcomprises a wavelength-division multiplexed (WDM) PBS network.
 4. Themethod of claim 1, wherein the GMPLS-based label includes an input fiberport field identifying an input fiber port of a node at a receiving endof the lightpath segment identified by the GMPLS-based label.
 5. Themethod of claim 1, wherein the GMPLS-based label includes at least onefield identifying an input wavelength employed for carrying signals overthe lightpath segment identified by the GMPLS-based label.
 6. The methodof claim 5, wherein the input wavelength is defined by a value stored inthe IEEE standard 754 single precision floating point format.
 7. Themethod of claim 6, wherein the input wavelength is based on a functionof a channel spacing variable, and the GMPLS-based label includes awavelength field and a channel spacing field to store a channel spacingvalue.
 8. The method of claim 1, wherein the method is performed by:selecting a selected lightpath route comprising a plurality of lightpathsegments coupled between the plurality of nodes, said lightpath routebeginning with a source node and ending with a destination node andincluding at least one switching node between the source and destinationnodes; traversing lightpath segments on the selected lightpath route;generating a GMPLS-based label for each lightpath segment; and employingthat GMPLS-based label for a corresponding lightpath segment to reservethat lightpath segment for the scheduled timeframe.
 9. The method ofclaim 8, wherein the method includes: determining, at each node alongthe selected lightpath route, whether the lightpath segment received atthat node and a corresponding network resource are available for useduring the scheduled timeframe; and reserving a network resource for agiven lightpath segment for the scheduled timeframe if it is available,otherwise providing indicia to the source node to indicate the networkresource for the given lightpath segment is unavailable for thescheduled timeframe.
 10. The method of claim 8, wherein the selectedlightpath route comprises a first selected lightpath route, the methodfurther comprising: selecting a second selected lightpath route;determining, at each node along the second selected lightpath route,whether the lightpath segment received at that node is available for useduring the scheduled timeframe; and reserving a given lightpath segmentfor the scheduled timeframe if it is available, otherwise providingindicia to the source node to indicate the given lightpath segment isunavailable for the scheduled timeframe.
 11. The method of claim 8,wherein the method includes: performing a forward traversal of theselected lightpath route from the source node to the destination node;determining, at each node along the forward traversal, whether thelightpath segment received at that node is available for use during thescheduled timeframe; and temporarily reserving a network resource for agiven lightpath segment for the scheduled timeframe with a softreservation if it is determined to be available; determining if all ofthe lightpath segments along the selected lightpath route and networkresources are available for use during the scheduled timeframe; andcommitting the soft reservations for each lightpath segment if it isdetermined that all of the lightpath segment network resources areavailable for use during the scheduled timeframe.
 12. The method ofclaim 11, wherein the soft reservation are committed by: performing areverse traversal of the selected lightpath route from the destinationnode back to the source node; setting the soft reservation correspondingto a given lightpath segment to a hard reservation as the nodecorresponding to that lightpath segment is encountered during thereverse traversal.
 13. The method of claim 1, wherein data correspondingto the reservation of the lightpath is stored in a reservation lookuptable, the method further comprising: sending a control burst, during agiven timeframe, across the optical switched network from a source nodeto a destination node; and looking up, in the reservation lookup table,appropriate lightpath segments via which the control burst is to berouted to traverse a lightpath linking the source and destination nodesbased on lightpath segment and resource reservations corresponding tothe given timeframe.
 14. A switching apparatus for use in an opticalswitched network, comprising: optical switch fabric, having at least oneinput fiber port and at least one output fiber port; and a control unit,operatively coupled to control the optical switch fabric, including atleast one processor and a storage device operatively coupled to said atleast one processor containing machine-executable instructions, whichwhen executed by said at least one processor perform operations,including: receiving a resource reservation request from a first node,said resource reservation request including a first generalizedmulti-protocol label-switching (GMPLS)-based label identifying a firstlightpath segment between the first node and the switching apparatus,which comprises a second node; and scheduling a coarse-grainedtime-reserved use of the first lightpath segment for subsequenttransmission of data via the first lightpath segment.
 15. The switchingapparatus of claim 14 wherein execution of the instructions furtherperforms the operations of: creating a second GMPLS-based labelidentifying a second lightpath segment between the switching apparatusand a third node; replacing the first GMPLS-based label in the resourcereservation request; and forwarding the resource reservation request tothe third node.
 16. The switching apparatus of claim 14, wherein theoptical switched network comprises a photonic burst switched (PBS)network.
 17. The switching apparatus of claim 16, wherein the opticalswitched network comprises a wavelength-division multiplexed (WDM) PBSnetwork; and the optical switching fabric provides switching of opticalsignals comprising different wavelengths carried over common fibers thatmay be respectively coupled to said at least one input fiber port andsaid at least one output fiber port.
 18. The switching apparatus ofclaim 14, wherein the first GMPLS-based label includes an input fiberport field identifying an input fiber port of the switching apparatuscorresponding to an end of the first lightpath segment.
 19. Theswitching apparatus of claim 14, wherein the first GMPLS-based labelincludes at least one field identifying a wavelength employed forcarrying signals over the first lightpath segment.
 20. The switchingapparatus of claim 19, wherein the input wavelength is defined by theIEEE standard 754 single precision floating point format.
 21. Theswitching apparatus of claim 20, wherein the input wavelength is basedon a function of a channel spacing variable, and the first GMPLS-basedlabel includes a wavelength field and a channel spacing field to store achannel spacing value.
 22. The switching apparatus of claim 14, whereinexecution of the instructions further performs the operation of storinga time-reserved use of the first lightpath segment that is scheduled ina reservation table maintained by the switching apparatus.
 23. Theswitching apparatus of claim 14, wherein said at least one processorincludes a network processor.
 24. The switching apparatus of claim 23,wherein said at least one processor further includes a controlprocessor.
 25. A machine-readable medium to provide instructions, whichwhen executed by a processor in a switching apparatus comprising a firstnode in an optical switched network, cause the switching node to performoperations comprising: receiving a resource reservation request from asecond node, said resource reservation request including a firstgeneralized multi-protocol label-switching (GMPLS)-based labelidentifying a first lightpath segment between the second node and theswitching apparatus; and scheduling a coarse-grained time-reserved useof the first lightpath segment for subsequent transmission of data viathe first lightpath segment.
 26. The machine-readable medium of claim25, wherein execution of the instructions further performs theoperations of: creating a second GMPLS-based label identifying a secondlightpath segment between the switching apparatus and a third node;replacing the first GMPLS-based label in the resource reservationrequest; and forwarding the resource reservation request to the thirdnode.
 27. The machine-readable medium of claim 25, wherein the opticalswitched network comprise a wavelength-division multiplexed (WDM)photonic burst switched (PBS) network.
 28. The machine-readable mediumof claim 25, wherein the first GMPLS-based label includes an input fiberport field identifying an input fiber port of the switching apparatuscorresponding to an end of the first lightpath segment.
 29. Themachine-readable medium of claim 25, wherein the first GMPLS-based labelincludes at least one field identifying a wavelength employed forcarrying signals over the first lightpath segment.
 30. Themachine-readable medium of claim 25, wherein execution of theinstructions further performs the operation of storing a time-reserveduse of the first lightpath segment that is scheduled in a reservationtable maintained by the switching apparatus.